1. Field of the Invention
The present invention relates to a yoke-type magnetoresistive (MR) head, a yoke-type MR composite film head, and a magnetic storage apparatus using the same.
2. Description of the Related Art
Recently, with the rapid development of the computer processing capability, a magnetic recording medium such a hard disk is desired to increase the data transfer rate. In order to realize this, a magnetoresistive type magnetic head has been playing a significant role.
Originally, the magnetic head using the magnetoresistive (MR) head was dedicated for production (information reading). However, the magnetic storage apparatus requires a head capable of not only reproduction but also recording (write in). For this, a shield type MR head and a yoke type MR head have been developed and examined.
In the shield type MR head as shown in FIG. 6 of Japanese Patent publication A63-205584, an MR pattern (magnetoresistive element) is sandwiched by a soft magnetic shield, and adjacent to the shield, an electromagnetic induction type recording head is arranged.
FIG. 17 is a cross sectional view showing a configuration of the conventional shield type MR head. In the conventional shield type MR head 101 an MR pattern (magnetoresistive element) 105 is arranged via an MR insulation layer 104 made from a non-magnetic material such as oxide and sandwiched by a lower shield layer 102 made from a soft magnetic material and a common pole 103 made from a soft magnetic material. The conventional shield type MR head 101 further includes an electromagnetic induction type recording head constituted by the common pole 103, an upper pole 106, and a coil pattern 107. One end of the MR pattern 105 is exposed to a head air bearing surface (ABS). The common pole 103 and the upper pole 106 are magnetically connected at their rear ends (opposite to the head ABS side). It should be noted that the reference symbol 108 denotes a non-magnetic layer made from an oxide or the like. This non-magnetic layer 108 constitutes a recording gap serving for electrical insulation between the coil pattern 107 and the common pole 103. The reference symbol 109 is a layer for covering a stepped portion. This stepped portion coverage layer coves a stepped portion formed by the coil pattern 107 and serves for electric insulation between the coil pattern 107 and the upper pole 106.
The yoke type MR head provides a hollow space at a portion of the yoke constituting the magnetic head and an MR pattern (magnetoresistive element) is arranged in the vicinity of this hollow space.
FIG. 18 is a cross sectional view showing a configuration of a conventional yoke-type MR head. The conventional yoke type MR head 201 includes a lower pole 202, an upper pole front part 203, an upper pole rear part 204, an MR pattern (magnetoresistive element) 205, and a coil pattern 206. The reference symbol 207 denotes a non-magnetic layer made from an oxide or the like. This non-magnetic layer 207 forms a gap between the lower pole 202 and the upper pole front part 203. The upper pole rear part 204 and the lower pole 202 are magnetically connected at the rear side (opposite to the head air bearing surface). The reference symbol 208 denotes a gap provided between the upper pole front part 203 and the upper pole rear part 204. The MR pattern 205 is arranged in the vicinity of this gap 208. The lower pole 202 and the upper pole rear part 204 are magnetically connected at the rear part (opposite to the head air bearing surface). Symbol 209 denotes a stepped portion coverage layer made from a non-magnetic material.
As shown in FIG. 18, in the conventional yoke type MR head 201, a gap 208 is present in a portion of the yoke pattern constituted by the lower pole 202, the upper pole front part 203, and the upper pole rear part 204. Accordingly, there is a defect that a magnetic flux cannot effectively pass through during recording. To eliminate this defect, Japanese Patent Publication A3-66015 suggests a composite type thin film magnetic head which includes a center pole (not depicted) in the vicinity of the gap 208, so as to increase the recording efficiency.
In the conventional shield type MR head as shown in FIG. 17, the MR pattern is partially exposed to the ABS plane (head air bearing surface) where the magnetic head faces a recording medium. Accordingly, when the recording medium is brought into contact with the MR pattern, the MR pattern generates a noise. This noise generation phenomenon is called thermal asperity. In a recent magnetic storage apparatus, in order to increase the recording density, the head flying height is minimized for the recording medium. When the head flying height is decreased, the medium is brought into contact with the head more frequently, often causing thermal asperity of the reproduction output. That is, in a higher density recording, thermal asperity noise tends to increase. For this, the magnetic storage apparatus using the conventional shield type MR head may lower reliability.
The cause of the thermal asperity in a reproduction signal of the conventional shield type MR head can be explained as follows. During a magnetic recording, the MR head and the medium relatively move at a high speed equal to above 10 m per second. Here, if the magnetic head flowing amount is small and is brought into contact with the MR pattern of the head, the collision generates a friction head so that the MR pattern temperature is instantaneously increased. When the MR pattern temperature is increased, its component, i.e., ferromagnetic metal thin film increase resistance. In a detection circuit reading an information item by converting into voltage the resistance change in the MR pattern signal magnetic field, the resistance change by heat generation is erroneously read as a signal. Moreover, the heated MR pattern has a great cooling time constant compared to an ordinary signal waveform. Until the MR pattern is cooled down, a great DC-like bias voltage is applied to the signal, which greatly shifts the detection level. This may cause a signal burst error.
Furthermore, another thermal asperity is involved. In the MR head a sense current is constantly applied to the MR pattern. For this, the MR pattern constantly generates some heat. When the medium is brought into contact with the MR pattern and the collision energy is not so large, the heat of the MR head moves to the medium, the MR pattern temperature is instantaneously lowered. This temperature lowering reduces the resistance of the MR pattern, which may cause a signal magnetic field detection error. In either case, the conventional shield type MR head has a configuration which easily cases the thermal asperity as a first problem.
The second problem of the shield type MR head is that the magnetic recording element and the reproduction element are not aligned at the same position on the ABS plane. Accordingly, the recording track position and the reproduction track position are slightly different. Consequently, the magnetic disk apparatus should have a servo circuit to correct the difference.
These first and second problems can be improved by the yoke type MR head shown in FIG. 18. In the yoke type MR head, in order to solve the problems of thermal asperity, the MR pattern is located at a position far from the ABS plane. This configuration allows to use the yoke as a recording head having a gap, and generation of the recording magnetic field is significantly low. On the other hand, with increase of the magnetic recording density, the coercive force Hc of the recording medium tends to be increased. This leads to a high magnetic field intensity from the magnetic head required for recording. However, the conventional yoke type MR head cannot generate a sufficiently high magnetic field intensity and is not preferable for a high density recording. This is a third problem.
The third problem is caused as follows. As shown in FIG. 18, in the yoke type MR head, the MR pattern 205 is provided at the gap 208 between the upper pole front part 203 and the upper pole rear part 204. The upper pole front part and the rear part serve as a yoke for the MR pattern. This yoke has a large heat capacity. Even if the tip end of the recording pole (ABS plane) collide against the recording medium, the heat generation is not transferred to the MR pattern. Accordingly, no thermal asperity is generated. However, since the yoke has the gap 208, and the magnetic resistance of the yoke is increased. For this, it is impossible to increase a magnetic flux for recording. Accordingly, it is also impossible to increase the gap generated magnetic field generated on the ABS plane. That is, the conventional yoke type MR head has a demerit that the recording capability is low.
Furthermore, the conventional yoke type MR head has a problem in the reproduction efficiency. It is usual that the upper and the lower yokes have reluctance almost identical to the reluctance of the MR pattern. Accordingly, as shown in FIG. 18, when the MR pattern and the upper and lower poles as a yoke are connected in series, the total reluctance is doubled compared to the upper and lower poles alone. When the reluctance is doubled, this decreases by half the signal magnetic flux flowing from the information pattern of the magnetic recording medium into the upper and lower pole. That is, the efficiency is lowered during reproduction, too.
It is therefore an object of the present invention to provide a yoke type magnetoresistive (MR) head and yoke type magnetoresistive composite thin film head having an improved recording characteristic and reproduction characteristic by eliminating gaps other than the gap for recording and reproduction, as well as a magnetic storage apparatus using the yoke type magnetoresistive composite thin film head.
The yoke type magnetoresistive head according to the present invention comprises an upper pole, a lower pole, and a magnetoresistive (MR) element, wherein a magnetic gap is formed between a front end of the upper pole and a front end of the lower pole, and a rear end of the upper pole and a rear end of the lower pole is magnetically connected to form a magnetic flux path; and the magnetoresistive element is arranged at a deeper position than the magnetic gap so that the upper pole and the lower pole are magnetically bridged via the magnetoresistive element.
In this yoke type MR head, the upper pole and the lower pole are magnetically bridged via the MR element, thus forming separate magnetic flow path, which enables reproduction of a magnetic recording information. Since both of the upper pole and the lower pole have no gap, when the yoke type MR head is used for recording, it is possible to increase the recording magnetic flux amount, thus increasing the recording capability.
According to another aspect of the present invention, there is provided a yoke type magnetoresistive (MR) head comprising an upper pole, a lower pole, a magnetoresistive element, and write-in coil, wherein a magnetic gap is formed between a front end of the upper pole and a front end of the lower pole, and a rear end of the upper pole and a rear end of the lower pole is magnetically connected to form a magnetic flux path; the magnetoresistive element is arranged at a deeper position than the magnetic gap so that the upper pole and the lower pole are magnetically bridged via the magnetoresistive element so as to form a separate magnetic flux path; and the write-in coil is arranged between the upper pole and the lower pole.
In this yoke type MR head, the upper pole and the lower pole are magnetically bridged, so as to form a separate magnetic flux flow path via the MR element. This separate magnetic flux flow path can be used for reproducing a magnetic recording information. Since both of the upper pole and the lower pole have no gap, when using the yoke type MR head for recording, it is possible to increase the magnetic flux amount for recording, thus increasing the recording capability.
According to still another aspect of the present invention, there is provided a yoke type magnetoresistive (MR) composite thin film head comprising a lower pole, a recording gap insulation layer, a coil pattern, and an upper pole, wherein between the lower pole and the upper pole, there is arranged a mesa pattern formed from an insulation material and having slopes, one of the slopes being arranged at a deeper position than a throat height of the recording gap, and this slope having a magnetoresistive sensing element; and the upper pole and the lower pole have no magnetic gap.
In this yoke type MR composite thin film head, the upper pole and the lower pole are bridged via the MR element, so as to form a separate magnetic flux flow path, which can be used for reproduction of a magnetic recording information. Since both of the upper pole and the lower pole have no gap in the midst of the poles, it is possible to increase the magnetic flux amount for recording, thus increasing the recording capability.
The MR sensing element provided on one of the slopes of the mesa pattern in contact with a lead pattern extending to another slope adjacent to the aforementioned slope, and connected to an electrode via the slope.
This configuration allows the lead pattern assured to be connected to outside circuits.
The coil pattern may be formed on the mesa pattern. By forming the coil pattern on the mesa pattern, it is possible to reduce the dimension in the front and rear direction of the yoke type MR composite thin film head.
Moreover, the coil pattern may be formed adjacent to the mesa pattern.
By arranging the coil pattern not on the mesa pattern, it is possible to reduce the dimension in the height direction of the yoke type MR composite thin film head. Furthermore, by forming the coil pattern 4 and the mesa pattern almost on the same plate, it is possible to minimize the stepped portion. This enables to reduce the plating frame forming photoersist thickness of the upper pole. This is advantageous for narrowing the tip end of the upper pole.
At least in one of the upper pole and the lower pole, a portion of the film farther from the magnetic gap than the mesa pattern slope having the MR sensing element may have a reduced thickness than the other portion.
By reducing the film thickness of the upper pole or the lower pole, it is possible to increase the reluctance of the upper pole and the lower pole in series. When the series reluctance is increased, the magnetic flux amount flowing in the MR pattern is increased. This increases the reproduction output of the MR pattern.
At least in one of the upper pole and the lower pole, a portion of the film farther from the magnetic gap than the mesa pattern slope having the MR sensing element may have a reduced magnetic permeability than the other portion.
By reducing magnetic permeability, it is possible to increase the reluctance of the upper and lower poles in series. As a result, the magnetic flux amount flowing into the MR pattern is increased, thus increasing the reproduction output of the MR pattern.
Furthermore, at least in one of the upper pole and the lower pole, a portion of the film farther from the magnetic gap than the mesa pattern slope having the MR sensing element may have a reduced magnetic permeability and an increased saturation magnetic flux density than the other portion.
By reducing the permeability in the upper and/or lower poles, the reproduction output of the MR pattern is increased. And by increasing the saturation magnetic flux density, it is possible to assure a recording capability.
The lower pole may have an indentation to define the throat height and a mesa pattern can be arranged in the indentation.
With this configuration, the MR pattern can be arranged in the vicinity of the throat height, which increases the ratio of the signal flux flowing into the MR pattern. Moreover, it is possible to reduce the dimension of the yoke type MR composite thin film head in the height direction, facilitating to reduce the track width.
Moreover, the lower pole may have an indentation to define the throat height and a mesa pattern is arranged in the indentation, after which the MR sensing element is arranged on a slope of the mesa pattern; the indentation is filled with a non-magnetic insulator and flattened; a gap insulation layer is formed; a front portion of the upper pole is formed; and then the coil pattern and the upper pole are formed.
With the aforementioned configuration, it becomes easy to form a plating frame of a narrow track width.
According to still another aspect of the present invention, there is provided a magnetic storage apparatus comprising a yoke type MR composite thin film head having a lower pole and an upper pole sandwiching a mesa pattern formed from an insulation material and having slopes, wherein one of the slopes is located at a deeper position than a throat height of a recording gap; an MR sensing element is provided on that slope; and the upper pole and the lower pole have no magnetic gap, the yoke type MR composite thin film head being mounted on a slider substrate, which is maintained above a disk-shaped magnetic recording medium and the disk-shaped magnetic recording medium is rotated for magnetic recording and reproduction.
By using the yoke type MR composite thin film head, it is possible to realize a magnetic storage apparatus without causing thermal asperity.
According to yet another aspect of the present invention, there is provided a magnetic storage apparatus comprising a yoke type MR composite thin film head having a lower pole and an upper pole sandwiching a mesa pattern formed from an insulation material and having slopes, wherein one of the slopes is located at a deeper position than a throat height of a recording gap; an MR sensing element is provided on that slope; and the upper pole and the lower pole have no magnetic gap, the yoke type MR composite thin film head being mounted on a head assembly, the head assembly is brought into contact with a traveling magnetic tape for magnetic recording and reproduction.
By using this yoke type MR composite thin film head, it is possible to realize a magnetic storage apparatus without causing thermal asperity.